Flow machine, slide ring seal thereof, body part for said slide ring seal and method of fastening said slide ring seal to said flow machine

ABSTRACT

Disclosed is a slide ring seal, which is used, for example, for sealing a shaft space of a centrifugal pump in relation to a pumping space thereof and to centering the mechanical seal and/or fastening the seal to the casing of the centrifugal pump and a body part used for the attachment. A feature of the disclosed seal, including at least one rotary slide ring unit, a body part by means of which the seal is attached to the casing, and at least one either separate counter ring unit or a counter ring unit stationarily attached to the body part, is that the body part is provided with inclined fastening means by means of which the body part ( 40, 40 ′) is tightened to the casing both axially and radially.

The present invention relates to a new kind of a mechanical seal, socalled slide ring seal used, for example, for sealing a shaft space of acentrifugal pump in relation to a pumping space thereof. The presentinvention especially relates both to fastening said mechanical seal to acasing or a cover of the casing of a flow machine, the flow machineitself and a body part of said slide ring seal, and a method offastening said slide ring seal to said flow machine.

In the following, a flow machine refers to a centrifugal pump, but itmust be born in mind that the term flow machine refers in connectionwith the present invention to all liquid treating apparatuses having arotary shaft, which is to be sealed in such a way that the liquid to betreated is not able to flow along the shaft out of the apparatus. Theprior art introduces, for example, slide ring seals, such as in FIG. 1,in which the slide ring seal used as shaft seal of a pump is typicallyfastened to a pump casing or a cover of said pump casing. Two or morehex screws, hex socket screws, or studs with nuts are used for attachingthe seal. The seal is typically radially positioned within the casing orwithin the cover of the casing by means of guidance between the casingor the cover of the casing and the body part of the seal and axiallyagainst the body part. The sealing water conduits required by the sealare generally positioned in a single acting seal in the casing or in thecover of the casing and in a double acting seal in connection with thebody/end part of the seal.

The shaft seal has always a separate fastening flange or a gland forfastening screws, in a single acting seal as well as in a double actingseal, located outside the body or end part of the seal. If the pumpcasing or the cover of the casing is considered, a prior art slide ringseal requires in addition to a relatively complicated seal constructionalso at least two bores for the fastening screws of the seal. Such astructure is relatively complicated and thus also expensive.

The present invention tends to eliminate at least some of the problemsof the prior art slide ring seals by tightening the seal directly to thecasing of the pump or to the cover of the casing without a separateflange part by fastening means operating preferably in an inclineddirection relative to the axis of the pump. By said fastening means, theseal is centered both radially against the guidance in the casing or inthe cover of the casing and axially against a shoulder or like arrangedin the cover of the casing or in the guidance of the casing or inconnection with any of them. In this way a complicated, expensive andalso unnecessary sealing gland is eliminated and moreover, the number ofbores required in the casing or cover of the casing is decreased.Accordingly, the seal becomes simpler and easier to assemble.

Other typical features of a slide ring seal, flow machine, body part ofsaid seal and a method of tightening said slide ring seal to said flowmachine in accordance with the invention become evident in theaccompanying claims.

The slide ring seal, flow machine, body part of said seal and the methodof tightening said slide ring seal to said flow machine are describedmore in detail below, with reference to the accompanying drawings, inwhich

FIG. 1 illustrates a slide ring sealing in accordance with the prior artas a shaft sealing of a centrifugal pump;

FIG. 2 illustrates a slide ring seal in accordance with a preferredembodiment of the present invention, a so called single acting seal, asa shaft sealing of a centrifugal pump, too; and

FIG. 3 illustrates a slide ring seal in accordance with anotherpreferred embodiment of the present invention, a so called double actingseal, as a shaft sealing of a centrifugal pump as well.

FIG. 1 illustrates a prior art slide ring seal arrangement of acentrifugal pump, by means of which arrangement a pumping space 12 inthe area of the impeller 10 of the centrifugal pump is separated fromthe shaft space 14 of the pump. The pumping space refers to all suchspace that is in a substantially open communication with the impeller10. In other words, the pumping space 12 covers areas both in front ofas well as behind the impeller 10. Exactly in the same way, the shaftspace 14 refers to a space, which is in direct communication with theshaft of the pump. In this case, the shaft space 14 is located betweenthe slide ring seal and the shaft 18. The seal arrangement naturallyprevents also the leaking of the liquid to be pumped from the pumpingspace to the atmosphere from between the casing 16 and the sealing. In aschematically illustrated arrangement in accordance with FIG. 1, themechanical seal comprises a rotary slide ring unit 24 positioned on theshaft 18 between the shoulder 20 of the shaft and the impeller 10, anon-rotary slide ring unit, i.e. a counterring unit, which is shown as afull assembly 26 with the body part of the seal and a fastening ring 30.The actual slide rings are shown by reference number 28. The abovedescription refers to slide ring units in general, because they areconventional technique and comprise a slide ring 28, a retainer ring,and possibly a spring device and/or a drive pin, O-ring, etc. Since thepresent invention does not profoundly relate to the inner structure ofthe slide ring unit, it is discussed more in detail neither here nor inconnection with the actual invention. Moreover, the sealing comprises anumber of O-rings 32 (shown in connection with a rotary slide ring unit,maybe found also in connection with the counter ring unit) or like sealsand retaining pins in the holes in the non-rotary slide ring unit and inthe body part, which pins are used for ensuring that the non-rotaryslide ring unit, i.e. counterring unit is not able to rotate with therotary slide ring unit 24. The seal also comprises a suitable springdevice, by means of which a suitable pressure is ensured between theslide ring pair 28. Further, the sealing comprises liquid conduits 36 inthe casing or in the cover of the casing 16. The actual attachment ofthe slide ring seal to the pump is carried out by axial bolts or studs38 extending to the casing 16. Two or more bolts, studs or screws arerequired for one seal. These screws, or more accurately the spacerequired for their opening, for their part, set requirements for thelength of the pump.

FIG. 2 illustrates a so called single acting slide ring seal inaccordance with a preferred embodiment of the invention, comprising muchthe same basic elements as the seal in accordance with the prior art.Same reference numbers are used for similar elements in both figures.However, if the description of the present invention is more profoundthan the description of the prior art, then new reference numbers willbe used for the corresponding elements, too. Further, it must be notedthat for simplicity, the following description discusses the casing ofthe flow machine, although the accurate term could as well be, forexample, the cover of the casing or seal casing.

In other words, the slide ring sealing in accordance with FIG. 2comprises, as for its rotary parts, a rotary slide ring unit 24 arrangedbetween a shoulder 20 of a shaft 18 and an impeller 10. The simplifiedillustration of said slide ring unit in the figure comprises in realityalso other elements, as is discussed already in the prior art section.The non-rotary parts of the slide ring sealing in accordance with theinvention comprise a body part 40 of the seal, which is guided againstthe inner surface of the casing 16 and a non-rotary counterring unit 42,which is guided against the inner surface of the body part 40. Ofcourse, in some cases, it is also possible that the non-rotarycounterring unit is not a unit separate from the body part, but isintegrated with the body part. Furthermore, the figure illustrates anumber of conventional sealing rings (e.g. so called O-rings), by meansof which, for example, the space between the casing 16 and the body part40 as well as the space between the body part 40 and the counterringunit 42 are sealed.

The axial and radial guidance of the seal in accordance with theinvention is carried out more precisely as follows. The substantiallyaxial and cylindrical inner surface of the casing 16 operates at leastsubstantially of the length, of which the body part 40 is in contactwith it in operation, as guiding surface 44, against which the body part40 is radially centered at a sufficient accuracy. Said guiding surface44 terminates to a shoulder 46, where the radius of the inner surface ofthe casing 16 is reduced. In other words, at the shoulder 46 the innersurface 44 of the casing 16 converges, when going farther away from theimpeller 10. A reduction in the radius of the body part 40 at a shoulder48 corresponds to said shoulder 46, whereby the axial positioning takesplace by means of said shoulders 46 and 48. The above described guidingis ensured by fastening or tightening the body part 40 to the casing 16by suitable means so that the fastening means forces both guidancessimultaneously against each other. Said fastening or tightening means ispreferably a screw 54 tightened into an inclined threaded hole 52 in thebody part 40 through an inclined hole 50 in the casing 16. Preferably,the screw 54 pulls the body part 40 against both the guiding surface 44and the shoulder 46 of the casing 16.

It is characteristic of the slide ring sealing in accordance with apreferred embodiment of the invention illustrated in FIG. 2 to have ashoulder 48 and a threaded hole 52 in the body part 40 of the seal. Itis characteristic of the shoulder 48 that by means thereof the seal ispositioned axially. When this goal is studied, it is understood that itmay be accomplished in addition to the illustrated conical shoulder,also by a radial shoulder or even so that the shoulder is replaced by anend surface of the body part, which takes its position against thecorresponding surface of the casing or against the corresponding surfacearranged in connection with the casing. However, the conical shoulderillustrated in the figure is still, in practice, the most preferredalternative. Another substantial element for the sealing in accordancewith the invention is, as previously mentioned, the threaded hole 52 inthe body part 40 of the seal, which is set in an inclined positioncompared to the axial and radial directions. The inclination of thethreaded hole 52 relative to the direction of the axis of the body partis of the order 5-85 degrees, preferably 15-75 degrees. Mostly saidthreaded hole is located in a plane running along the axis of the bodypart, but it is, of course, possible that for some reason the hole islocated in some other applicable plane. Thereby, the above mentionedinclination angle is determined by using a projection of the hole, andmore accurately of the axis thereof, onto a plane running both parallelto the axis of the hole and along the axis of the body part.

According to a preferred embodiment of the invention, the direction ofthe threaded hole is perpendicular to the conical shoulder surface ofthe body part, whereby the fastening screw extending to the threadedhole through the hole in the casing pulls the shoulder of the body partagainst the corresponding shoulder of the casing in a perpendiculardirection. It is substantial of the direction of the threaded hole 52and the hole 50 in the casing 16 that when tightening the screw 54 thebody part 40 of the seal tightens to its place both radially andaxially.

FIG. 3 illustrates a so-called double acting slide ring seal inaccordance with another embodiment of the invention. In fact, thestructure of the seal is very similar to the single acting sealillustrated in FIG. 2. The question is, in fact, about adding anotherpair of slide rings as a mirror image of the first one to the right sideof the seal of FIG. 2, i.e. to the side facing the pump bearings. Inother words, in the embodiment in accordance with FIG. 3, a first rotaryslide ring unit 24′ is arranged between the shoulder 20 of the shaft 18and the impeller 10, against which a non-rotary counter ring unit 42′,when going towards the bearing assembly of the pump is located, whichcounter ring unit 42′ is supported to the body part 40′ guided againstthe inner surface of the seal casing. A second rotary slide ring unit24″ is located to the right of the body part 40 between the counter ringunit 42′ and a second shoulder 64 on the shaft 18. In other words, onboth ends of the non-rotary counterring unit 42 there is provided aslide ring. In a manner exactly corresponding to the embodiment of FIG.2, the body part 40′ is axially supported by its shoulder against theshoulder in the casing 16 and radially against the guiding surface ofthe casing. The body part is also similarly fastened by means of a screwarranged in an inclined position into a hole 50 in the casing and into athreaded hole in the body part 40′. Thus, the variations shown inconnection with the single acting seal may also be applied in a doubleacting seal.

FIGS. 2 and 3 yet illustrate sealing water conduits, by which sealingwater lubricating the seal surfaces is supplied to the slide rings. InFIG. 2, a sealing water conduit 60 is located in the casing 16 of thepump or in the cover thereof so that it brings the liquid to the space12 between the seal and the casing, whereas in FIG. 3 a seal waterconduit 60′ brings the liquid through an opening 62 in the body part 40′of the seal via the channel arranged in the casing 16 to the space 14between the seal and the shaft 18. Naturally, in the embodiments of bothFIG. 2 and FIG. 3 there is also a second sealing water conduit, throughwhich the liquid is removed from the space, where it is brought to.

In addition to the manners illustrated in FIGS. 2 and 3, where the sealmay be installed and repaired at the end of the pump facing theimpeller, it is possible to apply the embodiment in accordance with theinvention also so that the seal may be assembled, removed or repaired atleast partially at the end of the pump facing the bearing assembly. Infact, the only changes that need to be done are the following. First, ashoulder will be arranged to the casing or to the cover of the casinglike the shoulder 48 in FIG. 2, but to the opposite side relative to thebody part of the seal, i.e. between the body part and the impeller. Thediameter of the casing or the cover of the casing in said shoulder isreduced towards the impeller so that the body part of the seal may bepushed against the shoulder to get the required axial support therefrom.The radial support is provided in the same way as in the previousembodiments along the guidance between the body part of the seal and thecasing or the cover of the casing. Of course, it would be possible toprovide this structure with an exactly similar inclined screw fasteningas in the embodiments of FIGS. 2 and 3, but in practice it is difficultto implement due to a relatively small axial dimensions of the casing,since the screw should be tightened to the body part of the seal fromthe direction of the impeller.

In other words, the tightening of the body part of the seal against theguiding surfaces is in the above embodiment preferably done in a mannerdifferent from the embodiments of FIGS. 2 and 3. Because the body partmust be pushed towards the impeller, for example, the tightening by ascrew must be made in an opposite manner. In this embodiment of theinvention, a the casing or the cover of the casing of the seal has beenprovided with a threaded hole into which a screw is tightened so thatthe screw pushes the body part of the seal towards the impeller, inother words against the above described shoulder of the casing or thecover of the casing. Simultaneously, the body part is also pushed by thescrew against the inner guiding surface of the casing or the cover ofthe casing on the side of the body part opposite to the screw. It istypical of this embodiment that it is not necessary to provide athreaded hole in the body part, but only a mere blind hole, a recess, asubstantially circumferential groove round the body part or acorresponding, but shorter groove is sufficient. It is thus acharacteristic feature of said fastening means that it operates togetherwith the preferably conical tip of the screw tightened to the threadedhole of the casing or the cover of the casing so that when tighteningthe screw deeper by means of said fastening means the screw tightens thebody part both axially and radially. Moreover it is worth mentioningthat the direction of the screw in the threaded hole of the casing or ofthe cover of the casing of the pump may be almost any including thedirection of the radius, because, for example, by a screw with a radialdirection and conical tip, it is also possible to carry out the inclinedtightening of the body part of the seal. Even then, the conical tip ofthe screw or the tip of the screw shaped in some other suitable mannertogether with the side surface or side edge of the groove, recess orhole accomplishes the tightening of the body part both axially andradially.

As can be seen from the above description it has been possible todevelop a slide ring sealing more simpler than the previous slide ringsealings. The slide ring sealing of the invention is also less expensiveand requires less space than the previous arrangements. While theinvention has been herein described by way of examples in connectionwith what are at present considered to be the preferred embodiments, itis to be understood that the invention is not limited to the disclosedembodiments, but is intended to cover various combinations and/ormodifications of its features and other applications within the scope ofthe invention as defined in the appended claims. With regard to theappended claims it has to be understood that the claims use a word‘housing’ by which all elements, parts, casings or casing covers,generally understood as points of application, to which the slide ringseal is to be fastened are covered.

1.-12. (canceled)
 13. A flow machine, comprising a rotary shaft (18) anda member (16) at least for the slide ring seal enclosing the shaft (18),characterized in that inclined fastening means (50) is arranged to saidmember (16) for tightening the slide ring seal to said member (16). 14.Flow machine in accordance with claim 13, characterized in that asubstantially cylindrical guiding surface (44) is arranged to the innersurface of said member for positioning the seal radially and that ashoulder (46) for positioning the seal axially is arranged at the innersurface of said member or at least in connection with said member. 15.Flow machine in accordance with claim 13, characterized in that saidfastening means is a non-threaded hole (50).
 16. Flow machine inaccordance with claim 13, characterized in that a slide ring seal isarranged inside said member (16), the body part (40, 40′) of which hasan inclined threaded hole (52).
 17. Flow machine in accordance withclaim 13, characterized in that said fastening means in the member (16)is a threaded hole.
 18. Flow machine in accordance with claim 17,characterized in that a slide ring seal is arranged inside said member(16), the body part of which has means for tightening the body partinside said member (16).
 19. Flow machine in accordance with claim 18,characterized in that said tightening means of the body part is a recessin the body part, a substantially circumferential groove or a blindhole.
 20. Flow machine in accordance with claim 13, characterized inthat an actuator used with the fastening and tightening means is a screw(54), by means of which a slide ring seal is tightened via its body part(40, 40′) to its housing both axially and radially.
 21. Flow machine inaccordance with claim 13, characterized in that a slide ring seal isarranged inside said member, in the body part (40, 40′) of which sealthere is a shoulder (48) or an end surface operating together with ashoulder (46) of the member(16) for positioning the seal inside saidmember (16).
 22. Flow machine in accordance with claim 13, characterizedin that said member (16) is a casing of a centrifugal pump or a cover ofthe casing.
 23. Flow machine in accordance with claim 13, characterizedin that a sealing water conduit (60, 60′) is arranged in the member (16)for supplying the sealing water to the slide ring seal.
 24. Flow machinein accordance with claim 13, characterized in that an opening (62) hasbeen arranged to the body part (40′) for supplying sealing water to ashaft space (14).
 25. A method of tightening a slide ring seal via itsbody part (40, 40′) to a member (16) surrounding a shaft (18) of a flowmachine, characterized in that said body part (40, 40′) is tightened tothe inside of said member (16) in such a way that the tightening takesplace concurrently both radially and axially.
 26. Method in accordancewith claim 25, characterized in that said tightening is carried out bypulling the body part (40, 40′) of the slide ring seal along the guidingsurface (44) in the member (16) in such a way that a shoulder (48) orlike of the body part (40, 40′) and a shoulder (46) or like of themember (16) are pressed against each other.
 27. Method in accordancewith claim 25, characterized in that said tightening is carried out bypushing the body part of the slide ring seal along the guide surface inthe member (16) in such a way that the shoulder or like of the body partand the shoulder of the member (16) are pressed against each other.